Heating apparatus of a workpiece of distorted shape, and a quenching apparatus for simultaneous operation of multiple cams and a quenching method for the same
1. Field of the Invention
The present invention relates to a heating apparatus for a workpiece of distorted shape used for a high-frequency heating apparatus and so on to perform uniform high-frequency heating of the periphery of the plate cam and so on, and to a quenching apparatus for simultaneous operation of multiple cams and a quenching method for the same to simultaneously heat peripheries of a set of cams with each different phase formed at a camshaft.
2. Description of the Prior Art
A typical high-frequency quenching apparatus for said apparatuses has performed heating by generating induced current on the periphery through supply of high-frequency electric current to a heating coil 910 from a transformer (not shown), while the cam 900 is rotated around a center 900A, in coincidence of a center 911A of a circular heating conductor 911 of a heating coil 910 heating the periphery of the cam 900 with a center 900A of the cam 900, as shown in FIG. 16. Such circumstances have been the same with camshafts formed with a set of cams with each different phase.
However, there is an essential disadvantage that a projecting part of the cam 900, that is, the most outer end 901 is suffered from concentrated induction heating, as it is in the closest vicinity to the heating conductor 911 of the heating coil 910, and, then, deeper quenching of it is performed, in comparison with that of other parts, as shown in FIG. 16(A). Especially, a heating coil 910, which has been used for all kinds of cams, has been used for high-frequency quenching, as a camshaft driving valves of an engine is formed with a set of cams with each different phase.
The above is not the best high-frequency quenching, and far from a solution for an essential disadvantage of concentrated heating of the most outer end 901.
Though there may be caused distortion, or quenching crack by ununiform heating, when deeper quenching of the most outer end 901 of the cam 900, than that of other parts, is performed, the above is not a problem proper to cams as a workpiece, but it is safe to say that the above is a common one to workpieces of distorted shape. And it has been pointed out that the problem is not only with high-frequency induction heating, but also with general resistance heating.
The present invention has been made under such circumstances. The object of the invention is to offer a heating apparatus for a workpiece of distorted shape to perform uniform heating of the periphery of the workpiece of distorted shape. Moreover, another object is to offer a quenching apparatus for simultaneous operation of multiple cams and a quenching method for the same to perform most suitable high-frequency quenching of each cam, without concentrated heating of each cam at the most outer end, even in the case of a camshaft formed with a set of cams with each different phase.
A heating apparatus of a workpiece of distorted shape according to the present invention performs relative rotation of a workpiece of distorted shape arranged at almost the center position of a heating coil and heats a periphery of the workpiece by the coil during the rotation, and is characterized in that it comprises a detector of an angle of rotation to detect a relative angle of rotation of the workpiece of distorted shape, and an electric power control part to control electric power to be supplied to the heating coil according to the detection results of the detector of an angle of rotation so that the most outer end at the most farthest position from the center of the workpiece of distorted shape are not excessively heated in comparison with other parts.
In such configuration, the electric power to be supplied to the heating coil is minimized, in the case of a state where the most outer end of the workpiece of distorted shape may be excessively heated by the heating coil, when the workpiece of distorted shape arranged at almost the center position of the heating coil is relatively rotated, and, as a result, the most outer end of the workpiece of distorted shape is not excessively heated.
If a relative angle of rotation of the workpiece of distorted shape is within a predetermined range around a standard angle as a center. The electric power control part may be preferably configured to minimize the electric power to be supplied to the heating coil, when the heating coil is a semiopen type coil, and a relative angle of rotation of the workpiece of distorted shape is assumed to be the standard angle, in a state where the most outer end of the workpiece of distorted shape is facing with the semiopen type coil and located on the perpendicular line passing through the center of the coil.
Moreover, if a relative angle of rotation of the workpiece of distorted shape is within a predetermined range around the standard angle as a center, the electric power control part may be preferably configured to minimize the electric power to be supplied to the heating coil, when the heating coil is a potbelly type coil with a configuration in which a semicircular small-diameter coil part is facing with a semicircular small-diameter coil part each other and they are jointed together, and a relative angle of rotation of the workpiece of distorted shape is assumed to be the standard angle, in a state where the most outer end of the workpiece of distorted shape is facing with the semicircular small-diameter coil part and located on the perpendicular line passing through the center of the coil part.
Another heating apparatus of workpiece of distorted shape according to the present invention has a basic configuration to perform rotation of a workpiece of distorted shape arranged at almost the center position of a circular coil and to heat a periphery of the workpiece by the coil during the rotation, and is characterized in that it comprises a motion mechanism to perform revolution of the workpiece of distorted shape around the circular coil or revolution of the circular coil around the workpiece of distorted shape, in a state where the center of the circular coil and that of the workpiece of distorted shape are deviated from each other, so that the periphery of the workpiece of distorted shape is uniformly heated.
In the case of such configuration, the distance between the periphery of the workpiece of distorted shape and the circular coil becomes uniform all over the periphery of the workpiece of distorted shape, and as a result, the periphery of the workpiece of distorted shape is uniformly heated by the circular coil, as the workpiece of distorted shape is rotated, and, at the same time, performs relative revolution to the circular coil.
When a workpiece of distorted shape is a plate cam, the radius r of the revolution of the plate cam or the circular coil may be preferably configured to be r≈(r1xe2x88x92r2)/2, when the workpiece of distorted shape is a plate cam, the distance between the most outer end in the most farthest position from the center of the plate cam and the center of the plate cam is assumed to be r1, and the distance between the other most outer end on the extension of the straight line connecting the both and the center of the plate cam to be r2.
A quenching apparatus for simultaneous operation of multiple cams according to the present invention is a quenching apparatus for simultaneous operation of multiple cams to perform simultaneous high-frequency quenching of peripheries of a plurality of kinds of cams with each different phase formed at a camshaft. And it has a configuration where a heating conductor to heat the peripheries of the cams comprises: a plurality of circular heating coils; transformers to supply electric current to the heating coils; a driving mechanism to perform revolution of the heating coils around the cams in a state where the centers of the heating conductors of the heating coils and those of the cams are deviated from each other; and a cooling mechanism to cool the heated cams, and electric currents are supplied from the same transformers to the heating coils with the same phase.
And, the radius r of the revolution of the heating coils may be preferably configured to be r≈(r1xe2x88x92r2)/2, when the distance between the most outer end in the most farthest position from the center of the cam and the center of the cam is assumed to be r1, and the distance between the other most outer end on the extension of the straight line connecting the both and the center of the cam to be r2.
A quenching method for simultaneous operation of multiple cams according to the present invention performs simultaneous heating of peripheries of a plurality of kinds of cams with each different phase formed at a camshaft, and heating conductors to heat the peripheries of the cams perform revolution motion of the heating coils around the cam in a state where the centers of the heating conductors of a plurality of circular heating coils are deviated from the centers of the cams each other, and electric currents are supplied from the same transformers to the heating coils with the same phase to heat the cams.
Moreover, the radius r of the revolution of the heating coils may be preferably configured to be r≈(r1xe2x88x92r2)/2, when the distance between the most outer end in the farthest position from the center of the cam and the center of the cam is assumed to be r1, and the distance between the other most outer end on the extension of the straight line connecting the both and the center of the cam to be r2.